Efficiency And Mechanism Of Algae Removal By Electrochemical Technology Using Activated Carbon Fiber/Nickel Foam Cathode

The pollution of algae blooms has seriously affected drinking water safety for a long time.The research taking microcystis aeruginosa the main kind of algae that forms algae outbreak as study subjects was conducted by Pt/Ti anode and ACF/Ni cathode.The efficiency and mechanism of Pt/Ti-ACF/Ni-Fe²⁺electrochemical algae removal system were investigated.In the experiment to explore the efficiency of Pt/Ti-ACF/Ni-Fe²⁺electrochemical algae removal system,the effects of Fe²⁺concentration,current density,electrode spacing and initial pH were investigated to determine its optimal working condition.In the optimal working condition,the indicator UV₂₅₄ was determined to reflect the change of organic matters in water during the electrolysis,OD₆₂₀ was determined to study the influence on the phycobiliprotein in the electrolysis and the concentration of MC-LR was determined to investigate the degradation of MC-LR in the electrolysis.The results showed that the optimal dosage of Fe²⁺in the range of 0 to 0.2 mmol/L was0.05mmol/L.The algae removal rate of this system increased with increasing current density and decreasing initial pH with a wide range of pH?3⁹?.The effect of electrode spacing in the range of 0.7cm to 2.0cm on algae removal was not obvious.During the electrolysis,the indicator UV₂₅₄ ascended in first and descended at last,and OD₆₂₀ kept going down,which manisfested that algal cells were destroyed and released intracellular organic matters,and it also showed the photosynthetic system of algal cells was damaged.In the process of electrolysis,the intracellular algal toxin MC-LR and other substances would be released into the extracellular environment and further degraded while the algal cells were ruptured.In the electrolysis,total algal toxin MC-LR showed a decreasing trend on the whole,and the concentration of extracellular MC-LR fluctuated within the maximum limit of 1.0?g/L.The removal process of algae by this system accorded with the first-order kinetic characteristics,moreover,the R² was 0.9852and the rate constant was 0.1829.In the research on the mechanism of Pt/Ti-ACF/Ni-Fe²⁺electrochemical algae removal system,based on the analysis of different electrochemical systems,analysis of hydroxyl radical?·OH?,comparative experiment with traditional Fenton experiment,SEM analysis of algal cells and cathode materials,FTIR,specific surface area and pore size analysis of ACF,the algal removal mechanism was explored.The results indicated that in this paper,the Pt/Ti-ACF/Ni-Fe²⁺partial heterogeneous cathode electrochemical Fenton algae removal system was constructed in the absence of oxygen supply facilities.Heterogeneous and homogenous electro-Fenton process were the main mechanism accompanied by electroadsorption,electroflocculation and electroflotation in the Pt/Ti-ACF/Ni-Fe²⁺algae removal system.In the initial reaction period,the electroadsorption was significant because of the sufficient adsorption sites.With the saturation of the adsorption sites,the electroadsorption was weakened intermittently during the reaction,and at this time,the desorbed algae floated on the surface due to the electroflotation.The removal rate in traditional Fenton was much lower and the electrochemical algal removal system can produce continuous Fenton oxidation effect.During the reaction in the system,the pH decreased rapidly to 3 approximately within1min and remained constant after that.The intracellular substances,the valence state of initial iron ion and the initial pH had no obvious influence on the pH during the reaction.The wide pH range in the system may be related to the hydrolysis of Fe³⁺,the decomposition side reaction of H₂O₂ and the generation of heterogeneous electrio-Fenton.In addition,electrolysis had little effect on the pore size distribution,specific surface area and pore volume of ACF.After electrolysis,almost no new functional groups was formed on the molecular bonds of ACF,and the surface morphology of ACF was not significantly changed.So the cathode materials maintained better stability and adsorbability,and could be reused.The paper provides a theoretical basis for the technology of electrochemical algae removal using ACF/Ni cathode,offers an efficient and environmentally friendly electrochemical algae removal technology,and has significant meaning for drinking water safety and dealing with the problem of algae blooms.